WWRT300N and VoIP setup

Question

I used a NR041 for 5 years and had a Cisco 7960 IP phone cabled behind it.  I upgraded to a WRT300N.  The install process did not support the setup for the IP phone.  I used the web access to insert a DMZ static address for the phone so the set up was the same as the NR041.  It did not work.  I also tried port 2000 forwarding but that did not work either.
The phone connects, has a dial tone, rings, etc. with the Cisco call manager.  But audio comomg in to the phone never connects.  The audio out from the phone works just fine.  The inbound audio cannot find the phones address behind the router.  Port forwarding and DMZ are supposed to help this.  
The only thing that has changed is the router.  What is the proper set up for the 7960 on the WRT300N?   

Answer 1

That is the same advice the chat session advisor gave me.  I did downloaded the current version, loaded it via the router administration web page, reset the router via the administration web page, did a power cycle and then ran the Easy Link Advisor to reconfigure the router.  Then I went in to reset the WEP key and set the DMZ.  That still did not resolve the issue.
I redid the process a second time and this time used port forwarding (2000)  and that did not work either.
I will redo the full cycle again with the DMZ setting.  
This does bring up another question.  The Linksys download page identifies the date for the most recent version of the firmware as June 4, 2007 for version 1.51.2.   The router web page "status" the version as 1.51.2 with date stamp of Feb 27, 2007.  This has occured with both down loads identified above.  The same date stamp issue occurs on the WPC300N PC card driver downloads.  I think someone forgot to updae the internal date in the software to match the release date on the web page.  However the chat session advisor did not think that was correct.  Perhaps someone has the correct answer.